Mobile communication systems were developed to provide mobile users with communication services. With the rapid advance of technologies, the mobile communication systems have evolved to the level capable of providing high speed data communication service beyond the early voice-oriented services.
Recently, standardization for a Long Term Evolution (LTE) system, as one of the next-generation mobile communication systems, is underway in the 3rd Generation Partnership Project (3GPP). LTE is a technology for realizing high-speed packet-based communications with the data rate of up to 100 Mbps, which is higher than the currently available data rate.
To meet the demand for wireless data traffic having increased since deployment of 4G communication systems, efforts have been made to develop an improved 5G or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘Beyond 4G Network’ or a ‘Post LTE System’. The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems. In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud Radio Access Networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), reception-end interference cancellation and the like. In the 5G system, Hybrid FSK and QAM Modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed.
The Internet, which is a human centered connectivity network where humans generate and consume information, is now evolving to the Internet of Things (IoT) where distributed entities, such as things, exchange and process information without human intervention. The Internet of Everything (IoE), which is a combination of the IoT technology and the Big Data processing technology through connection with a cloud server, has emerged. As technology elements, such as “sensing technology”, “wired/wireless communication and network infrastructure”, “service interface technology”, and “Security technology” have been demanded for IoT implementation, a sensor network, a Machine-to-Machine (M2M) communication, Machine Type Communication (MTC), and so forth have been recently researched. Such an IoT environment may provide intelligent Internet technology services that create a new value to human life by collecting and analyzing data generated among connected things. IoT may be applied to a variety of fields including smart home, smart building, smart city, smart car or connected cars, smart grid, health care, smart appliances and advanced medical services through convergence and combination between existing Information Technology (IT) and various industrial applications.
In line with this, various attempts have been made to apply 5G communication systems to IoT networks. For example, technologies such as a sensor network, Machine Type Communication (MTC), and Machine-to-Machine (M2M) communication may be implemented by beamforming, MIMO, and array antennas. Application of a cloud Radio Access Network (RAN) as the above-described Big Data processing technology may also be considered to be as an example of convergence between the 5G technology and the IoT technology.
In line with the completion of the LTE standardization, an LTE-Advanced (LTE-A) system is now under discussion, which improves a data rate by adopting the LTE communication system with several new technologies. One of such technologies is Carrier Aggregation. The Carrier Aggregation is a technology allowing a User Equipment (UE) to use multiple downlink carriers and multiple uplink carriers, unlike the conventional technology of using one downlink carrier and one uplink carrier, for data communication.
The current release of LTE-A specifies only an intra-evolved Node B (intra-eNB) carrier aggregation. This diminishes the applicability of carrier aggregation function and is likely to cause carrier aggregation failure especially in a scenario where a plurality of pico cells and one macro cell coexist. In order to solve this problem, a new study item called ‘small cell enhancement’ is being discussed in 3GPP Rel-12. This study item aims to enable inter-eNB carrier aggregation technique for guaranteeing a high data rate to a UE by aggregating the serving cells belonging to the different eNBs or dual connectivity technique (hereinafter, these techniques are referred integrally to as ‘dual connectivity’). Although other mobility-related fields are being discussed actively, the dual connectivity technique, which allows carrier aggregation between macro and pico (or small) cells, is likely to affect significantly to the future communication technologies. With the increase of the mobile data traffic due to the widespread use of the smartphone, it is expected that the market share of the small cell eNBs capable of accommodating UEs independently increases along with the small cell deployment using legacy Remote Radio Head (RRH). In the case that a UE connects to a small cell for data communication, it may receive other types of data from the macro eNB simultaneously.
Since the transmit power of the UE is determined depending on the type of the UE in the legacy communication system, the eNB receives the UE headroom power report periodically or according to an event (e.g. pathloss) and manages uplink resource of the UE efficiently based thereon. In the case that the UE is transmitting uplink data at the maximum allowed power, although the eNB which is not aware thereof increases the uplink radio resource for the current UE, the UE cannot use corresponding resource efficiently due to the lack of transmit power. In the mobile communication system supporting the dual connectivity, it is necessary for the UE to report the transmit power information for a plurality of eNBs respectively unlike the legacy UE reports the transmit power information to a single eNB. However, the current standard does not specify any transmit power reporting scheme of the UE operating in the inter-eNB carrier aggregation or dual connectivity mode and therefore there is a need of a method of reporting the transmit power report of a UE operating in the dual connectivity mode.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.